Preheat the oven to 425 Fahrenheit.
Mix dry ingredients: In a large bowl mix the dry ingredients - flour, salt, baking powder and baking soda. Use a whisk to mix everything well.
Mix wet ingredients: Melt butter. Let it cool until it is not too hot to touch. To the slightly cooled butter add eggs, milk, and vanilla. Whisk together until it is well combined.
Fold everything together: Add the fruit of your choice to the flour mixture to briefly coat with a light layer of flour. Then add the egg mixture into the bowl with flour. Use a spatula to stir the batter together, about 12 folds, just until everything is incorporated. Do not over-stir.
Scoop & bake: Add about ⅓ cup of batter to fill each muffin cup. Place the muffin tin in the preheated oven to bake for 8 minutes. Then turn the oven to 475 and bake another 5-8 minutes until fully baked. Remove muffins from the oven when they spring back from the touch and when the center does not look gooey.
Cool & store: Wait for the muffins to cool slight (just a few minutes), then remove them from the muffin pan. Let them sit on a cooling rack until fully cool. Then place in a container lined with a paper towel (this will absorb any fruit moisture), keep in a cool dry place and eat within 3-4 days.